Cobalt-rich wear resistant alloy and method of making and use thereof

ABSTRACT

A cobalt-rich wear resistant and corrosion resistant alloy useful for parts of a combustion engine such as valve seat inserts includes, in weight % about 0.1 to about 0.8% C, about 0.1 to about 1.5% Mn, about 3 to about 5% Si, about 10 to about 20% Cr, about 5 to about 32% Fe, about 0.5 to about 4% W, about 10 to about 30% Mo, up to about 20% Ni, about 20 to about 40% Co, up to about 6% V, up to about 3% Nb, total V plus Nb of about 0.5 to about 8.5% and balance unavoidable impurities including up to 0.035% P, up to 0.015% S and up to 0.250% N.

FIELD OF THE INVENTION

The present invention relates to wear resistant alloys useful forapplications such as valve seat inserts of internal combustion engines.

BACKGROUND

In the field of internal combustion engines, iron-based alloys andnickel-based alloys have been developed for engine parts such as valveseat inserts. Although there has been some development of cobalt-basedalloys for such applications, fewer cobalt-based alloy systems have beencommercialized due to the high cost of cobalt. Although cobalt-basedalloys have the potential for achieving required heat resistance,corrosion resistance and wear resistance of VSI applications, there is aneed for lower cost cobalt-based alloys suitable for VSI applications.

SUMMARY

Disclosed herein is a cobalt-rich alloy (referred to herein as “J580”)useful for VSI applications wherein the alloy comprises, in weightpercent (%), about 0.1 to about 0.8% C, about 0.1 to about 1.5% Mn,about 3 to about 5% Si, about 10 to about 20% Cr, about 5 to about 32%Fe, about 0.5 to about 4% W, about 10 to about 30% Mo, up to about 20%Ni, about 20 to about 40% Co, up to about 6% V, up to about 3% Nb, totalV plus Nb of about 0.5 to about 8.5%, balance unavoidable impuritiesincluding up to 0.035% P, up to 0.015% S and up to 0.250% N.

In an embodiment, the cobalt-rich alloy comprises, in weight percent(%), about 0.18 to about 0.52% C, about 0.7 to about 1.2% Mn, about 3.5to about 4.6% Si, about 11 to about 15% Cr, about 16 to about 27% Fe,about 1 to about 1.5% W, about 19 to about 23% Mo, about 0.7 to about 4%Ni, about 26 to about 36% Co, about 1.3 to about 4% V, about 1.2 toabout 2.3% Nb, balance unavoidable impurities including up to 0.035% P,up to 0.015% S and up to 0.250% N.

The cobalt-rich alloy can have a bulk hardness which exhibits less than10% hardness variation as a function of tempering below 1500° F.

The cobalt-rich alloy can have a vanadium content of about 1.3 to about3.6% which solution phase matrix with optional Laves phase. Thecobalt-rich alloy can include MC type carbide formers such as V and Nbin an amount of up to about 9 wt. %, such as about 0.5 to about 8.5 wt.% or about 3 to about 5 wt. %.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph of bulk harness as a function of tempering temperaturefor several J580 alloy compositions.

FIG. 2 shows a correlation between measured bulk hardness and calculatedbulk hardness.

FIG. 3 is a graph of radial crush toughness as a function of temperingtemperature for several J580 alloy compositions.

FIG. 4 shows a correlation between measured radial crush toughness andcalculated radial crush toughness.

FIG. 5 is a graph of radial crush toughness versus bulk hardness.

FIGS. 6-8 are graphs of dimensional change versus temperature whereinFIG. 6 is a graph of dimensional change versus temperature for J3, FIG.7 is a graph of dimensional change versus temperature for J10, and FIG.8 is a graph of dimensional change versus temperature for J580.

FIG. 9 is a graph of compressive yield strength versus temperature forseveral J580 alloy compositions for J580, J3, J10 and J153.

FIG. 10 is a graph of ultimate tensile strength versus temperature forseveral J580 alloy compositions for J580, J3, J10 and J513.

FIG. 11A and FIG. 11B are scanning electron micrographs (SEM) of a J580alloy composition.

FIG. 12A and FIG. 12B are scanning electron micrographs of a J10 alloycomposition.

FIGS. 13-15 show Plint wear test results for J10 and three J580 alloyswherein FIG. 13 shows pin specimen wear, FIG. 14 shows plate specimenwear, and FIG. 15 shows total materials wear.

FIG. 16 shows bulk hardness versus temperature data for various J580alloys.

FIG. 17 shows radial crush toughness versus temperature data for variousJ580 alloys.

FIG. 18 shows UTS versus test temperature for various J580 alloys.

DETAILED DESCRIPTION

Disclosed herein is a cobalt-rich alloy (referred to herein as “J580” or“J580 alloy”). The J580 alloy is designed as a cost effective alloywhich exhibits wear resistance and corrosion resistance along with animproved thermal shock resistance and machinability. The J580 alloy canexhibit desirable hardness, microhardness, and hardness distribution ina casting component, such as a valve seat insert (“VSI”).

In developing the J580 alloy, various alloy compositions were evaluatedfor mechanical properties and microstructure. The J580 alloy compositioncan be tailored to achieve desired mechanical properties of VSIs such asbulk hardness, radial crush strength, dimensional change, compressiveyield strength, tensile rupture strength, corrosion resistance, and wearresistance. To achieve desired performance objectives of VSIs, the J580alloy composition can be tailored to provide a microstructure having acobalt solid solution phase, eutectic phases, Laves phase, and MC typecarbides. For example, the J580 alloy can have a microstructure with twoprimary matrix phases (lamellar shaped eutectic reaction phases andLaves phases) and fine MC type carbides for strengthening. Cobalt canform intermetallic phases with molybdenum and Sigma phase with chromium,iron can form intermetallic phases with molybdenum and chromium, andsilicon can form intermetallic phases with cobalt, molybdenum, chromiumand iron. In addition, nickel can be added to form inclusions to reducethe grain size of the matrix phase. Thus, in the J580 alloy, the alloyelements and ranges can be controlled to form intermetallic phases inaddition to the Laves phase in the matrix to reduce the volume percentof cobalt solid solution phase by controlling the iron and siliconadditions to the J580 alloy. Compared to the J10 alloy (a Co-base alloyavailable from L.E. Jones, the assignee of the present application)having about 60% cobalt and a matrix of about 50 vol. % Laves phases andabout 50 vol. % cobalt solid solution phases, the J580 alloy which has amuch lower Co content, can provide a VSI having a more homogenizedmicrohardness distribution across a component cross section.

Table 1 summarizes experimental J580 heats for various alloycompositions. Six of the heats were adopted to make a standard VSI testrings for some basic materials testing including temper response, bulkhardness, radial crush toughness, and corrosion. The basic geometricdimensions of the test VSI samples are: 1.935″ (49.15 mm) OD, 1.570″(39.88 mm) ID, and 0.3020″ (7.67 mm) in height.

TABLE 1 Summary of J580 Alloy Compositions in Weight % Heat No. C Si MnNi Cr Mo W V Co Fe P S Nb 8E11XC 0.485 4.19 0.71 3.42 12.06 21.74 1.303.97 27.03 22.97 0.024 0.005 1.67 8E04XB 0.185 4.40 0.95 0.95 14.8122.12 1.45 3.57 29.67 19.21 0.026 0.004 2.26 8E04XA 0.187 3.84 0.95 0.7414.83 21.89 1.39 3.79 30.93 19.08 0.027 0.005 1.95 8E03XB 0.508 4.350.82 3.44 12.39 21.56 1.25 3.57 27.39 22.67 0.023 0.006 1.59 8E03XA0.481 4.29 0.80 3.53 11.86 21.58 1.29 4.25 26.52 23.34 0.023 0.005 1.608C22XB 0.447 4.62 0.71 3.20 13.51 21.78 1.20 1.30 35.45 16.13 0.0240.006 1.25 8C22XA 0.489 4.45 0.76 3.16 13.91 21.44 1.17 1.52 35.08 16.460.025 0.005 1.16 8B15XA 0.362 4.85 0.80 3.38 13.29 21.42 1.25 1.57 36.1215.20 0.026 0.005 1.38 8B13XA 0.412 4.45 0.99 0.53 19.29 19.38 1.33 3.7728.74 20.57 0.022 0.004 0.10 8A16XB 0.444 4.58 1.06 0.78 13.95 22.591.35 3.35 30.31 19.21 0.025 0.004 1.97 8A16XA 0.404 4.35 1.01 0.82 13.8423.35 1.33 3.43 29.60 19.75 0.024 0.004 1.70 8A05XB 0.416 4.56 1.15 2.7013.41 18.98 1.05 2.15 26.61 27.12 0.025 0.003 1.36 8A05XA 0.430 4.211.10 3.55 12.35 22.22 1.05 2.02 28.68 22.63 0.025 0.003 1.32 7L19XA0.379 4.37 0.93 0.92 13.21 22.75 1.43 3.08 37.31 13.66 0.026 0.004 1.617L12XB 0.353 4.57 0.95 0.91 13.29 22.75 1.42 3.08 37.20 13.54 0.0260.004 1.59 7L12XA 0.514 3.57 0.98 3.92 11.80 21.25 1.06 1.84 28.55 24.520.024 0.004 1.52 7L09XA 0.526 3.92 1.13 3.94 11.16 21.12 1.07 1.87 28.4424.82 0.024 0.003 1.54

The J580 alloys listed in Table 1 have about 0.18 to about 0.55% C,about 3.5 to about 5% Si, about 0.2 to about 1.2% Mn, about 11 to about20% Cr, about 13 to about 28% Fe, about 1 to about 1.5% W, about 18 toabout 23% Mo, about 0.5 to about 4% Ni, about 26 to about 38% Co, about1.5 to about 4.3% V, about 0.1 to about 2.3% Nb, balance unavoidableimpurities including up to 0.035% P, up to 0.015% S and up to 0.250% N.

VSI ring samples were made using six of the heats (8E04 XB, 8E03XB,8C22XB, 8A16XB, 8A05XB, 7L12XA) listed in Table 1. These six VSI ringsamples were evaluated for bulk hardness and radial crush strength. Perthe alloy design concepts, the bulk hardness of J580 within the alloyingelemental ranges investigated did not show significant hardnessvariation as a function of tempering temperature when the temperature isbelow 1500° F. The tempering response tested using the samples made ofthe six heats (see Table 1) confirmed that there was no significant bulkhardness variation (as a non-allotropic system) in the J580 alloy heats.Nevertheless, it has been clearly demonstrated that several alloyingelements had significant influences to J580 alloy system in terms of thelevel of bulk hardness can be achieved. With an assumption that cobaltand iron together can be treated as a combination of “primary matrixelements” in J580 alloy system, then, the effect of carbon, nickel,chromium, molybdenum, and vanadium to bulk hardness has been analyzed.Applying a linear regression method, Equation 1 provides an estimate ofthe average bulk hardness as a function of several alloying elements canbe expressed as:HRc_(bulk)=71.6378+6.34391C−2.16431Ni−1.30782Cr+0.591747Mo−3.12869V  Equation1:

The test results for bulk hardness measurements as a function oftempering temperature are shown in FIG. 1. Table 2 lists the bulkhardness values for the six samples at various tempering temperatures.FIG. 2 shows a correlation between measured bulk hardness and calculatedbulk hardness.

TABLE 2 Hardness Measurement Results Versus Tempering TemperatureTempering Temperature Bulk Hardness (HRc) ° F. ° C. 7L12XA 8A05XB 8A16XB8C22XB 8E03XB 8E04XB 72 22 53.5 53.0 59.0 57.0 54.9 57.9 800 427 53.752.3 58.7 57.3 55.1 57.8 900 482 53.9 53.5 59.0 57.3 55.1 57.7 1000 53853.4 52.9 59.0 57.4 55.4 57.6 1050 566 53.7 52.7 58.7 57.5 55.2 58.01100 593 53.3 52.8 59.0 57.1 55.7 57.2 1150 621 53.9 51.9 58.9 57.5 55.558.1 1200 649 53.2 53.1 58.1 57.2 55.4 57.4 1250 677 52.7 52.6 58.4 57.455.5 58.3 1300 704 52.6 52.3 58.2 57.6 55.6 58.5 1350 732 52.9 53.3 58.357.7 55.6 57.5 1400 760 53.8 53.2 59.0 57.4 55.7 57.6 1450 788 53.0 52.458.9 57.4 56.1 58.0 1500 816 53.1 52.9 58.9 57.5 55.2 57.6 Average 53.352.8 58.7 57.4 55.4 57.8

Table 3 summarizes the radial toughness measurement results for sixheats of J580. The radial crush toughness as a function of temperingtemperature for all six heats evaluated is shown in FIG. 3. As with therelationship between bulk hardness and tempering temperature, the radialcrush test as a function of tempering temperature showed a similar trendfor each heat involved. For a mathematic simulation purpose, an averageradial crush test toughness index is applied to perform this linearregression study. Equation 2 provides an estimate of the radial crushtoughness simulation results for J580 alloy system wherein alloyingelements such as carbon, nickel, chromium, and vanadium are effective toenhance the toughness while molybdenum exhibits a negative effect toJ580 radial crush toughness. In Equation 2, RCT is radial crushtoughness. FIG. 4 shows a correlation between measured RCT andcalculated RCT.RCT=−1.55+0.265C+0.0683Ni+0.11Cr−0.00935Mo+0.0955V  Equation 2:

TABLE 3 Radial Crush Toughness Versus Tempering Temperature TemperingTemperature Radial Crush Toughness Index (8.33 × 10⁻² ft-lb) ° F. ° C.7L12XA 8A05XB 8A16XB 8C22XB 8E03XB 8E04XB 72 22 0.337 0.312 0.200 0.2850.272 0.124 800 427 0.314 0.337 0.216 0.248 0.261 0.121 900 482 0.3250.298 0.204 0.263 0.256 0.128 1000 538 0.294 0.292 0.180 0.244 0.2800.132 1050 566 0.309 0.359 0.186 0.279 0.277 0.128 1100 593 0.342 0.3310.189 0.265 0.251 0.128 1150 621 0.339 0.351 0.188 0.265 0.247 0.1311200 649 0.331 0.342 0.197 0.270 0.268 0.127 1250 677 0.316 0.341 0.2040.262 0.248 0.121 1300 704 0.342 0.338 0.207 0.269 0.213 0.142 1350 7320.327 0.309 0.210 0.314 0.254 0.163 1400 760 0.361 0.315 0.202 0.2790.259 0.146 1450 788 0.383 0.314 0.182 0.247 0.228 0.126 1500 816 0.3270.327 0.209 0.275 0.216 0.141 Average 0.332 0.326 0.198 0.269 0.2520.133

For the J580 alloy system, the average radial crush toughness andaverage bulk hardness from ambient through 1500° F. (816° C.) showed areasonably good correlation which can be expressed by Equation 3 (below)where Y represents average radial crush toughness and “x” representsaverage bulk hardness.Y=0.0009x ²−0.1221x+4.3741.  Equation 3:

Within a bulk hardness range (HRc 50 to HRc 65) which is of mostinterest for the intended alloy applications, the radial crush toughnessindex value was within a range of 0.17 to 0.35 (8.33×10² ft-lb) which isa suitable range for the intended alloy application. It is hinted byEquation 3, that an increase in bulk hardness of J580 decreases theradial crush toughness but at a non-linear and slower rate than theincrement rate of bulk hardness. FIG. 5 shows a correlation between bulkhardness and RCT.

Dimensional stability tests were conducted to evaluate the J580 Alloy.The dimensional stability test conditions include 20 hours heat soakingat 1200° F. followed by slow air cooling for the J580 alloy evaluation.The outer diameter (“OD”) dimension was measured prior to and after thethermal treatment from two perpendicular radial orientations. For thedimensional stability test, an OD dimensional change smaller than 0.0005inches is considered PASS. Table 4 summarizes the dimensional stabilitytest results. It is clearly demonstrated that a sound dimensionalstability is possessed in the J580 alloy.

TABLE 4 Dimensional Stability Test Results OD Dimensional MeasurementResults (inch) Material: Reading Reading Reading Reading J580 BeforeBefore After After Heat Thermal Thermal Thermal Thermal Δ in Δ in Result8E03XB Treatment Treatment Treatment Treatment Reading Reading (Pass orSample at 0° at 90° at 0° at 90° at 0° at 90° Fail) 1 1.93850 1.937601.93850 1.93780 0.00000 0.00020 Pass 2 1.93830 1.93840 1.93820 1.93845−0.00010 0.00005 Pass 3 1.93830 1.93810 1.93825 1.93810 −0.00005 0.00000Pass 4 1.93790 1.93870 1.93790 1.93865 0.00000 −0.00005 Pass 5 1.938201.93840 1.93820 1.93830 0.00000 −0.00010 Pass Average 1.93824 1.938241.93821 1.93826 −0.00003 0.00002 Pass * Thermal soaking condition - 20hours at 1200° F.

Table 5 summarizes the dilatometry analysis results for five heats ofthe J580 alloy along with typical thermal expansion coefficient forcobalt-based VSI alloys J3 and J10 (both available from L. E. Jones, theassignee of this application). It is clearly shown that the J580 heatspossess similar CTEs as the J3 and J10 cobalt-based alloys. Thetemperature increment (or decrement) rate was 3°/min for all the tests.The information in Table 5 indicates that alloying elementalconcentration investigated can affect thermal expansion and contractionbehavior but the variations observed are relatively small. One of theprimary factors affecting the level of thermal expansion and contractionbehavior in the J580 alloy is the combined matrix elements, cobalt andiron along with the ratio of cobalt to iron.

TABLE 5 Thermal Expansion Coefficient For J3, J10, J580 Alloys in mm/mm°C.: Reference Reporting Temperature Temperature (° C.) (° C.) 7L12XA7L12XB 8A05XA 8A16XA 8B13XA J3 J10 25 100 12.2 11.2 12.2 11.6 11.7 10.910.6 25 200 12.8 11.7 12.9 12.8 12.8 12.1 11.6 25 300 13.1 12.0 13.213.1 13.1 12.5 11.9 25 400 13.3 12.3 13.4 13.2 13.3 12.9 12.2 25 50013.6 12.6 13.6 13.4 13.5 13.2 12.5 25 600 14.0 12.9 13.9 13.7 13.9 13.412.8 25 700 14.3 13.3 14.1 14.0 14.4 13.9 13.3 25 800 14.5 13.6 14.314.3 14.8 14.3 13.7 25 900 14.7 13.8 14.5 14.4 15.1 14.3 14.0 25 100014.9 14.1 14.6 14.4 15.4 14.4 14.2

From on-heating and on-cooling behavior among J3 (FIG. 6), J10 (FIG. 7),and J580 (FIG. 8), it is evident that J10 and J580 showed similarbehavior while J3 showed a slightly different behavior in terms ofdimensional changing rate between on-heating and on-cooling portion of athermal exposure. The space separating on-heating and on-cooling curveshown in J3 indicates that a significant permanent deformation has takenplace during on-heating thermal soaking. On the contrary, J10 and J580showed a very small gap between on-heating and on-cooling curves that isan indication of stable microstructures and no significant solid statephase transformation has taken place. From a general VSI dimensionalstability consideration, the dimensional gap at the ambient afterheating then cooling cycle is an indicator of an alloy dimensionalstability for VSI applications.

Compressive yield strength and tensile strength were evaluated for theJ580 alloy. Compressive yield strength is a desired property for VSIapplications. Compared to an iron-based or nickel-based alloy,especially for iron-based alloys with martensitic or ferriticmicrostructures, there is a threshold temperature at which compressiveyield strength tends to drop rapidly. One goal of the J580 alloy is toachieve sustained compressive yield strength comparable to nickel basealloys by forming a combined “iron+cobalt” base within a fully solidstate temperature range. FIG. 9 shows a comparison of compressive yieldstrength as a function of temperature among J3, J10, J513, and J580.J580 (X75, Heat 8C22XA) showed a very good compressive yield strengthswithout rapid drop behavior within a range up to 650° C. and, thecompressive yield strength of J580 is generally greater than J3 withinthat temperature range.

In evaluating tensile strength of the J580 alloy, it was found thatAlloy J580 (X75, Heat 8C22XA) showed a sustained tensile rupturestrength up to 650° C. It is at the lower end of the tensile strengthband of the four alloys discussed. However, the tensile rupture strengthcurve as a function of temperature has clearly exhibited a sound tensileproperty that only slightly varies with testing temperature up to 650°C. The tensile rupture strength behavior can be beneficial to VSIapplications due to lower potential stress concentration induced byalloy microstructural distribution. A comparison of ultimate tensilerupture strength for alloys J580, J3, J10, and J513 is depicted in FIG.10.

In an evaluation of corrosion resistance, VDA immersion and condensatecorrosion tests were conducted with very strong mixed acids with a pHvalue at 1.2 and majority of the testing cycle (6 out of 7 days)includes holding test cell at 50° C. For the 1.2 pH test, the testingsolution was made based upon standard VDA test solution composition. Forthe 2.8 pH test, an L.E. Jones (LEJ) test solution was applied includingsodium sulfate: 7800 ppm SO₄ ⁻²; sodium nitrate: 1800 ppm NO₃ ⁻ which isadjusted with acetic acid (˜5 g/L) for obtaining 2.8 pH. The testingcycle and procedure for the 2.8 pH test is identical to the 1.2 pH test.Among the group of VSI alloys evaluated, J580 along with J10, J133 andJ153 possessed the lowest corrosion rate. Essentially, no corrosioncould be measured from immersion testing or condensate testing for thesefour alloys.

For the 2.8 pH immersion and condensate corrosion tests, J580 againshowed no measureable corrosion rate.

FIGS. 11A-B and FIGS. 12A-B show typical SEM microstructural morphologyfor J580 and J10, respectively. It should be noted that J580 showedsignificant high oxidation resistance and, it took more than 15 hours toetch with LEJ etchant to show the detail of the solidificationsubstructure. However, some interdendritic areas (between Laves phaseand eutectic phases) were etched out under the etching condition. On theother hand, J10 sample could be etched in a relative shorter time toshow its microstructure. In addition, it should be noted that themagnification of FIGS. 11A-B and FIGS. 12A-B is different and micronmarkers are attached with these photos. Therefore, J580 possesses asignificantly finer microstructure than J10 including the size of Lavesphase. J10 is a Co-base alloy with about 60% Co, about 28% Mo, about 8%Cr, and about 2.5% Si. In FIG. 11B, Areas 1, 2 and 3 show Laves phases,Area 4 shows eutectic phases, and Area 5 shows an etched out area.Compared to J10, the Si content of the Laves phase in J580 issignificantly higher than the Si content of the Laves phases of J10.

Experiments were carried out to evaluate castability of J580 andevaluate properties of J580 compared to J3 and J10 alloys available fromL.E. Jones Co. The compositions of samples evaluated are set forth inthe Table 6 below wherein “Rem” refers to remainder of unavoidableelements:

TABLE 6 J580 (Nos. 1-5), J3 and J10 Alloy Compositions No. Co Mo Cr FeSi Ni V Mn Nb W C Rem. 1 36 22 13 13 5 5 1 0.8 1 1 0.3 Bal 2 39 27 13 135 1.75 0.8 1.25 1.25 0.3 Bal 3 35 22 13 13 5 5 1 0.8 1 1 0.3 Bal 4 35 2613 13 5 1.75 0.8 1.25 1.25 0.3 Bal 5 35 23 16 15 5 1.75 0.8 1.25 0.3 BalJ3 50 30 1.5 0.5 0.3 0.3 13 2.4 Bal J10 60 28.5 8 2.4 Bal

The J580 alloys listed in Table 6 have about 0.3% C, 5% Si, 0.8% Mn,13-16% Cr, 13-15% Fe, 1-1.25% W, 22-27% Mo, 0-5% Ni, 35-39% Co, 1-1.75%V, 1-1.25% Nb, balance unavoidable impurities including up to 0.035% P,up to 0.015% S and up to 0.250% N.

The following Table 7 sets forth bulk hardness (HRC), peak load (lbf),deformation (inch) and radial crush toughness (8.33 ft-lb) for thesamples tested.

TABLE 7 Mechanical Properties of J580 Heats 1-3 and J10 Radial CrushHeat Bulk Hardness Peak Load Deformation Toughness 1 53 1463.8 0.02740.401 2 58.5 1066.8 0.0228 0.244 3 52 1357.6 0.0263 0.357 J10 57 6310.0196 0.124

As shown above, J580 exhibits similar hardness to J10 but J580 exhibitsbetter radial crush toughness. The alloys for Heats 1-3 and J10 werecast and examined. It was found that the 580 alloy exhibits a morehomogenized (uniform) microhardness distribution compared to J10 whereasboth samples exhibited similar bulk hardness. The more evenlydistributed microhardness for J580 appears to be due to the finermicrostructural distribution (both cobalt solid solution phase and Lavesphase) compared to that of J10.

The J580 alloy compositional system can be designed to form a compositeof Co—Fe face centered cubic (FCC) phase, Co—Mo—Cr—Si rich Laves phase,and small amount of carbides. A J580 sample made of Heat 8E11XB was usedto conduct an x-ray diffraction assisted phase characterization. Thisheat was specifically made to examine a lower end of cobalt content(27.0 wt. %) for the alloy system. In addition, a higher end of ironcontent (23.5 wt. %) was also examined. The ratio of cobalt to iron is1.15. The phase characterization was carried out with a SmartLab x-raydiffractometer at Rigaku and; the disk block samples with 1.25″ indiameter and ½″ of thickness were prepared at L. E. Jones. Both cobaltradiation and copper radiation sources were applied for this experimentand; with cobalt radiation, the x-ray diffraction spectrum resolutionwas significantly better than that with copper.

Two different crystalline phase quantification methods (DD and RIR) wereapplied and both methods were in agreement upon the identification offour major crystalline phases namely, FCC (austenite), MoFe₂ Lavesphase, Martensite, and Mo₆Co₆C carbides. Considering the results fromboth DD and RIR methods, the heat sample contains greater than 59% andup to 74% FCC phase and 4.9% to 13.0% martensitic phase. Therefore, theamount of austenite (FCC) plus martensite together is more than 72% or78.9%. This is higher than the desired/expected value for the alloysystem.

In the evaluation of Heats 1-3, Heat 1 was found to exhibit abinary-phase matrix and the total amount of MC carbide formers isapproximately 3 wt. %. Heat 2 was found to exhibit a three-phase matrixand the total amount of carbide formers is approximately 4.25%. Heat 3was found to exhibit a three-phase matrix and the total amount ofprimary MC type carbide formers is approximately 3%. Heat 3 exhibits athree-phase domain solidification substructural distribution similar toHeat 2 but with over two times more Fe than Heat 2.

The microstructures of Heats 1-3 can be summarized as follows: Heat 1has about 34 vol. % primary intermetallic and about 66 vol. % Co solidsolution; Heat 2 has about 24 vol. % secondary intermetallic, about 48vol. % primary intermetallic and about 28 vol. % C solid solution; andHeat 3 has about 37 vol. % secondary intermetallic, about 45 vol. %primary intermetallic and about 18 vol. % Co solid solution.

Plint wear tests summarized in Table 8 were carried out with threedifferent heats of J580 alloy samples paired with Crutonite valvematerial. A standard Plint testing condition including 20N applied load,20 Hz reciprocating frequency, 1 mm stroke length, and 100,000 totaltesting cycles. The test temperatures for each materials pair include23° C., 50° C., 100° C., 150° C., 200° C., 250° C., 300° C., 350° C.,400° C., 450° C. and 500° C. The mass change of both pin and platespecimens were determined by weighing pin and plate specimens before andafter a test.

TABLE 8 Summary of Plint Wear Test Results J580 J580 J580 TemperatureJ10 (8A16XA) (8E03XA) (8E04XA) (° C.) (1J10A) X75-4 X75-6 X75-7 PinSpecimen Wear 23 0.4 0.5 0.2 0.6 50 0.6 0.9 0.6 0.8 100 0.6 0.8 0.7 0.9150 0.9 0.9 1.1 1.0 200 1.1 0.9 1.2 1.0 250 1.0 1.0 1.1 1.1 300 1.4 1.11.5 1.2 350 1.9 0.4 1.1 1.0 400 1.4 0.3 0.6 0.3 450 0.8 0.2 0.5 0.1 5000.3 0.0 0.0 0.0 Plate Specimen Wear 23 1.6 1.4 1.2 1.2 50 1.0 1.4 1.41.0 100 1.0 1.1 1.4 1.0 150 1.2 1.2 1.4 1.2 200 1.2 1.1 2.3 1.5 250 1.41.3 2.3 1.8 300 1.0 1.5 2.7 2.4 350 0.5 1.2 2.0 2.5 400 0.8 1.0 2.0 1.6450 1.2 0.5 1.5 0.9 500 0.7 0.5 0.6 0.6

The Plint wear test results for pin, plate, and total materials wear asa function of testing temperature are shown in FIG. 13, FIG. 14 and FIG.15, respectively wherein Curves A-D correspond to alloys J10 (1J10A),J580 (8A16XAA), J580 (8E03XA), and J580 (8E04XA), respectively. Amongfour materials pairs tested for this project, three are related to J580pin materials (three different heats) and one is related to J10 pinmaterial. All the plate specimens were extracted from Crutonite valves.All four materials pairs, in general, showed a reasonable pin to platewear ratio for engine valvetrain applications along with amount ofmaterials wear based upon general L. E. Jones Plint wear test criteria.Comparatively, the overall best wear resistance is from J580 (8A16XA) vsCrutonite materials pair.

Fourteen additional alloy compositions and HRc test results are setforth in the following Table 9. Table 10 provides bulk hardness versustempering temperature data for seven of the alloys listed in Table 9.

TABLE 9 Examples of J580 Alloy Compositions in Weight % Heat No. C Si MnNi Cr Mo W V Co Fe Nb HRc 9A02XA 0.482 3.88 0.356 1.17 20.21 28.35 1.545.29 29.80 7.34 1.13 60.3 9A03XA 0.308 4.41 0.249 4.18 14.08 22.26 2.261.76 33.19 16.08 0.60 57.0 9A03XB 0.520 4.49 0.406 4.92 13.28 22.31 2.013.79 22.26 24.06 1.32 57.1 9A03XC 0.520 4.49 0.465 6.94 13.27 21.82 2.334.14 20.82 23.22 1.33 50.6 9A03XD 0.520 4.39 0.366 8.84 13.43 21.96 2.194.16 22.71 19.46 1.32 54.3 9A04XA 0.560 4.57 0.345 10.58 13.45 22.293.24 3.97 21.46 17.98 1.30 47.4 9A04XB 0.570 4.42 0.386 12.03 13.8521.70 3.24 3.82 20.56 17.86 1.09 49.2 9B05XA 0.530 3.71 0.570 0 13.3119.02 2.30 4.71 22.07 31.27 1.79 58.8 9B05XB 0.212 5.02 0.520 0 13.3023.73 1.58 1.39 33.30 19.07 1.32 56.7 9B06XA 0.530 4.24 0.357 12.3113.92 22.31 3.24 3.31 21.37 15.68 2.05 51.5 9B22XA 0.540 4.07 0.31312.40 13.92 23.29 3.24 3.26 21.48 15.82 2.00 48.8 9C15XA 0.355 4.720.224 17.04 15.39 22.71 3.22 1.52 21.35 12.16 0.66 50.8 9C15XB 0.2964.76 0.286 9.80 14.95 22.52 2.91 1.62 25.89 15.70 0.63 53.6 9C15XC 0.3124.63 0.312 0 14.74 22.26 2.57 1.80 34.37 17.64 0.65 59.4

TABLE 10 Summary of bulk hardness as a function of tempering temperatureTemper Temperature Bulk Hardness vs Tempering Temperature (HRc) (° F.)9A02XA 9A03XA 9A03XB 9A03XC 9A03XD 9A04XA 9A04XB 72 61.4 57.8 57.6 55.054.9 49.2 49.2 800 61.0 57.6 57.3 54.7 55.2 49.9 49.4 900 61.2 57.5 57.655.0 55.2 49.6 49.9 1000 61.4 57.4 57.8 53.5 54.9 49.2 49.5 1050 61.757.4 57.7 53.3 55.0 49.3 49.3 1100 61.1 57.5 57.7 54.0 54.9 49.1 49.51150 61.4 57.3 57.6 53.4 54.9 49.2 49.2 1200 61.2 57.3 57.5 54.3 55.248.8 49.2 1250 61.0 57.5 57.3 54.4 55.2 48.6 48.8 1300 61.3 57.4 57.554.6 54.0 49.3 49.5 1350 60.7 57.7 57.5 55.1 55.0 48.7 49.2 1400 61.257.5 57.6 55.2 54.9 49.1 49.2 1450 61.5 57.3 58.0 54.9 54.9 49.5 48.91500 61.8 57.7 57.8 53.7 54.6 50.0 48.8

The J580 alloys listed in Table 9 have about 0.2 to about 0.6% C, about3.5 to about 5% Si, about 0.2 to about 0.6% Mn, about 13 to about 20%Cr, about 7 to about 32% Fe, about 1 to about 1.5% W, about 19 to about29% Mo, 0 to about 17% Ni, about 20 to about 35% Co, about 1.3 to about5.3% V, about 0.6 to about 2.1% Nb, balance unavoidable impuritiesincluding up to 0.035% P, up to 0.015% S and up to 0.250% N.

The bulk hardness data listed in Table 10 is depicted in FIG. 16 whereinCurves A-G correspond to alloys 9A02XA, 9A03XA, 9A03XB, 9A03XC, 9A03XD,9A04XA and 9A04XB, respectively. The test results indicate thattempering temperature does not significantly affect bulk hardness forthe J580 heats tested.

Table 11 lists the results of radial crush toughness (RCT) testing onalloys 9A02XA, 9A03XA, 9A03XB, 9A03XC, 9A03XD, 9A04XA and 9A04XB. FIG.17 illustrates the RCT test data wherein Curves A-G correspond to alloys9A02XA, 9A03XA, 9A03XB, 9A03XC, 9A03XD, 9A04XA and 9A04XB, respectively.As shown, heat 9A03XA exhibited the highest overall radial crushtoughness compared to the other heats tested.

TABLE 11 Summary of radial crush toughness vs tempering temperatureTemper Temperature Radial Crush Toughness (8.33 × 10⁻²) (° F.) 9A02XA9A03XA 9A03XB 9A03XC 9A03XD 9A04XA 9A04XB 72 0.311 0.285 0.210 0.1930.205 0.176 0.184 800 0.207 0.348 0.213 0.184 0.213 0.191 0.196 9000.139 0.324 0.210 0.162 0.217 0.184 0.200 1000 0.159 0.301 0.211 0.1840.227 0.185 0.209 1050 0.173 0.250 0.192 0.220 0.203 0.189 0.192 11000.173 0.342 0.203 0.189 0.186 0.187 0.176 1150 0.175 0.274 0.204 0.1750.216 0.199 0.206 1200 0.189 0.348 0.281 0.196 0.225 0.205 0.204 12500.227 0.256 0.230 0.174 0.230 0.177 0.179 1300 0.254 0.256 0.217 0.2060.222 0.176 0.182 1350 0.224 0.245 0.224 0.195 0.214 0.187 0.207 14000.170 0.273 0.206 0.196 0.245 0.199 0.217 1450 0.194 0.265 0.219 0.2020.248 0.211 0.226 1500 0.181 0.280 0.188 0.268 0.283 0.183 0.217

Multiple linear regression was made using bulk hardness and radial crushtoughness as a function of alloying elements for the J580 alloy. Forbulk hardness, Equations 4 and 5 were obtained from the regressionprocess wherein the elements in parenthesis represent the amount of eachelement:HRc=−479+57.0(C)−11.8(Mn)+15.0(Si)+5(Ni)+10.7(Cr)+0.65(Mo)−5.15(W)+1.13(V)+5.6(Co)+5.3(Fe)+11.8(Nb).  Equation4:RCT=−0.1038−2.283(C)+1.478(Mn)−0.1123(Si)+0.03739(Ni)−0.07174(Cr)+0.09685(Mo).  Equation5:

As shown in Equation 5, increasing Mn, Ni and Mo and/or lowering C, Siand Cr contents can increase the radial crush toughness.

Five Experimental Heats, 8A05XA, 8B13XA, 8C22XA, 8E03XA, and 8E04XA weretested to evaluate tensile rupture strength. The compositions andtensile test results for these heats are summarized in Table 12 andTable 13, respectively. Iron contents of these J580 heats are within arange of about 16 to about 24 wt. %. In comparison to the J580 alloy,commercial TRIBALOYS T400 and T800 have a substantially lower ironcontent (<3 wt. %) along with much higher cobalt content (60 wt. % Coand 51 wt. % Co for T400 and T800, respectively) as listed in Table 14.

TABLE 12 Composition of Experimental Heats Heat C Si Mn Ni Cr Mo W V CoFe S Nb 8A05XA 0.430 4.21 1.10 3.55 12.35 22.22 1.05 2.02 28.68 22.630.003 1.32 8B13XA 0.412 4.45 0.99 0.53 19.29 19.38 1.33 3.77 28.74 20.570.004 0.10 8C22XA 0.489 4.45 0.76 3.16 13.91 21.44 1.17 1.52 35.08 16.460.005 1.16 8E03XA 0.481 4.29 0.80 3.53 11.86 21.58 1.29 4.25 26.52 23.340.005 1.60 8E04XA 0.187 3.84 0.95 0.74 14.83 21.89 1.39 3.79 30.93 19.080.005 1.95 The P contents of the above alloy heats were 0.025%, 0.022%,0.025%, 0.023% and 0.027%, respectively.

TABLE 13 Summary of Tensile Rupture Strength Results Test TemperatureUTS (ksi) ° F. 8A05XA 8B13XA 8C22XA 8E03XA 8E04XA 72 85.6 55.2 99.8 64.021.4 200 81.9 56.0 90.7 55.6 41.6 400 72.9 44.5 79.6 50.7 23.1 600 71.054.8 106.6 52.8 29.4 800 69.5 48.7 92.5 52.1 41.1 1000 80.3 55.6 90.659.3 31.4 1100 75.4 58.6 88.3 64.5 18.9 1200 80.8 38.5 110.2 51.6 8.1

TABLE 14 Nominal Composition of Commercial Tribaloys T400 and T800 Co CrMo Si at % at. % at. % at. % C Alloys (wt. %) (wt %) (wt. %) (wt %) (wt%) Others T400 Bal. 10.4 18.8 5.9 (<0.1) Ni, Fe  (8.5) (28.5) (2.6) T800Bal. 20.8 18.4 7.7 (<0.1) Ni, Fe (17.5) (28.5) (3.5)

The J580 alloys listed in Table 12 have about 0.18 to about 0.5% C,about 3.8 to about 4.5% Si, about 0.7 to about 1.1% Mn, about 11 toabout 20% Cr, about 16 to about 24% Fe, about 1 to about 1.4% W, about19 to about 23% Mo, about 0.5 to about 4% Ni, about 26 to about 35% Co,about 1.5 to about 4.3% V, about 0.1 to about 2% Nb, balance unavoidableimpurities including up to 0.035% P, up to 0.015% S and up to 0.250% N.

For the intended alloy applications, the ultimate tensile strength (UTS)is preferably equal to or greater than 50.0 ksi at ambient and elevatedtemperatures is preferred. Referring to Tables 11 and 12, when the C+Sicontent is greater than 4.86 wt. %, it is possible to achieve 50.0 ksiUTS from ambient through 1200° F. Therefore, the carbon+silicon contentin Heat 8E04XA will not achieve the preferred 50 ksi UTS. In addition,to achieve 50 ksi UTS, the carbon content should be greater than 0.187wt. %. FIG. 18 plots UTS versus test temperature for heats 8A05XA (CurveA), 8B13XA (Curve B), 8E03XA (Curve C), 8E04XA (Curve D), and 8C22XA(Curve E). The effect of low carbon and carbon plus silicon on reducingthe tensile rupture strength of the J580 alloy system can be seen byCurve D in FIG. 18.

Based on the properties of Heat 8B13XA, in order to attain the preferred50 ksi UTS, several conditions must be met: (1) adding a predeterminedamount of carbon; (2) adding a predetermined amount of carbon plussilicon; and/or (3) adding a predetermined amount of niobium. Forexample, a preferred niobium content is within a range of about 1.60 wt.% to about 1.95 wt. % in order to obtain a UTS greater than 50 ksi at1200° F.

The J580 alloy includes C, Mn, Si, Cr, Fe, W, Mo, V and/or Nb, Co,optional Ni, and unavoidable impurities. In general, the J580 alloy caninclude: C in any amount falling within the range of 0.1 to 0.8%, Mn inany amount falling within the range of 0.1 to 1.5%, Si in any amountfalling within the range of 3 to 5%, Cr in any amount falling within therange of 10 to 20%, Fe in any amount falling within the range of 5 to32%, W in any amount falling within the range of 0.5 to 4%, Mo in anyamount falling within the range of 10 to 30%, Ni in any amount fallingwithin the range of 0 to 20%, Co in any amount falling within the rangeof 20 to 40%, V in any amount falling within the range of 0 to 6%, Nb inany amount falling within the range of 0 to 3%, total V plus Nb in anyamount falling within the range of 0.5 to 8.5%, balance unavoidableimpurities including up to 0.035% P, up to 0.015% S and up to 0.250% N.For example, the J580 alloy can include C in any amount falling withinthe ranges of 0.1-0.2%, 0.2-0.3%, 0.3-0.4%, 0.4-0.5%, 0.5-0.6%,0.6-0.7%, or 0.7-0.8%; Mn in any amount falling within the ranges of0.1-0.2%, 0.2-0.3%, 0.3-0.4%, 0.4-0.5%, 0.5-0.6%, 0.6-0.7%, 0.7-0.8%,0.8-0.9%, 0.9-1.0%, 1.0-1.1%, 1.1-1.2%, 1.2-1.3%, 1.3-1.4%, or 1.4-1.5%;Si in any amount falling within the ranges of 3.0-3.1%, 3.1-3.2%,3.3-3.4%, 3.4-3.5%, 3.5-3.6%, 3.6-3.7%, 3.7-3.8%, 3.8-3.9%, 3.9-4.0%,4.0-4.1%, 4.1-4.2%, 4.3-4.4%, 4.4-4.5%, 4.5-4.6%, 4.6-4.7%, 4.7-4.8%,4.8-4.9%, or 4.9-5.0%; Cr in any amount falling within the ranges of10-11%, 11-12%, 12-13%, 13-14%, 14-15%, 15-16%, 16-17%, 17-18%, 18-19%,or 19-20%; Fe in any amount falling within the ranges of 5-6%, 6-7%,7-8%, 8-9%, 9-10%, 10-11%, 11-12%, 12-13%, 13-14%, 14-15%, 15-16%,16-17%, 17-18%, 18-19%, 19-20%, 20-21%, 21-22%, 22-23%, 23-24%, 24-25%,25-26%, 26-27%, 27-28%, 28-29%, 29-30%, 30-31%, or 31-32%; Win anyamount falling within the ranges of 0.5-0.6%, 0.6-0.7%, 0.7-0.8%,0.8-0.9%, 0.9-1.0%, 1.0-1.1%, 1.1-1.2%, 1.2-1.3%, 1.3-1.4%, 1.4-1.5%,1.5-1.6%, 1.6-1.7%, 1.7-1.8%, 1.8-1.9%, 1.9-2.0%, 2.0-2.1%, 2.1-2.2%,2.3-2.4%, 2.4-2.5%, 2.5-2.6%, 2.6-2.7%, 2.7-2.8%, 2.8-2.9%, 2.9-3.0%,3.0-3.1%, 3.1-3.2%, 3.3-3.4%, 3.4-3.5%, 3.5-3.6%, 3.6-3.7%, 3.7-3.8%,3.8-3.9%, or 3.9-4.0%; Mo in any amount falling within the ranges of10-11%, 11-12%, 12-13%, 13-14%, 14-15%, 15-16%, 16-17%, 17-18%, 18-19%,19-20%, 20-21%, 21-22%, 22-23%, 23-24%, 24-25%, 25-26%, 26-27%, 27-28%,28-29%, 29-30%, 30-31%, 31-32%, 32-33%, 33-34%, 34-35%, 35-36%, 36-37%,37-38%, 38-39%, or 39-40%; Ni in any amount falling within the ranges of0-1%, 1-2%, 2-3%, 3-4%, 4-5%, 5-6%, 6-7%, 7-8%, 8-9%, 9-10%, 10-11%,11-12%, 12-13%, 13-14%, 14-15%, 15-16%, 16-17%, 17-18%, 18-19%, or19-20%; Co in any amount falling within the ranges of 20-21%, 21-22%,22-23%, 23-24%, 24-25%, 25-26%, 26-27%, 27-28%, 28-29%, 29-30%, 30-31%,31-32%, 32-33%, 33-34%, 34-35%, 35-36%, 36-37%, 37-38%, 38-39%, or39-40%; V in any amount falling within the ranges of 0-0.1%, 0.1-0.2%,0.2-0.3%, 0.3-0.4%, 0.4-0.5%, 0.5-0.6%, 0.6-0.7%, 0.7-0.8%, 0.8-0.9%,0.9-1.0%, 1.0-1.1%, 1.1-1.2%, 1.2-1.3%, 1.3-1.4%, 1.4-1.5%, 1.5-1.6%,1.6-1.7%, 1.7-1.8%, 1.8-1.9%, 1.9-2.0%, 2.0-2.1%, 2.1-2.2%, 2.3-2.4%,2.4-2.5%, 2.5-2.6%, 2.6-2.7%, 2.7-2.8%, 2.8-2.9%, 2.9-3.0%, 3.0-3.1%,3.1-3.2%, 3.3-3.4%, 3.4-3.5%, 3.5-3.6%, 3.6-3.7%, 3.7-3.8%, 3.8-3.9%,3.9-4.0%; 4.0-4.1%, 4.1-4.2%, 4.3-4.4%, 4.4-4.5%, 4.5-4.6%, 4.6-4.7%,4.7-4.8%, 4.8-4.9%, 4.9-5.0%, 5.0-5.1%, 5.1-5.2%, 5.3-5.4%, 5.4-5.5%,5.5-5.6%, 5.6-5.7%, 5.7-5.8%, 5.8-5.9%, 5.9-6.0%; Nb in any amountfalling within the ranges of 0-0.1%, 0.1-0.2%, 0.2-0.3%, 0.3-0.4%,0.4-0.5%, 0.5-0.6%, 0.6-0.7%, 0.7-0.8%, 0.8-0.9%, 0.9-1.0%, 1.0-1.1%,1.1-1.2%, 1.2-1.3%, 1.3-1.4%, 1.4-1.5%, 1.5-1.6%, 1.6-1.7%, 1.7-1.8%,1.8-1.9%, 1.9-2.0%, 2.0-2.1%, 2.1-2.2%, 2.3-2.4%, 2.4-2.5%, 2.5-2.6%,2.6-2.7%, 2.7-2.8%, 2.8-2.9%, or 2.9-3.0%; total V plus Nb in any amountfalling within the ranges of 0.5-1.0%, 1.0-1.5%, 1.5-2.0%, 2.0-2.5%,2.5-3.0%, 3.0-3.5%, 3.5-4.0%, 4.0-4.5%, 4.5-5.0%, 5-5.5.0%, 5.5-6.0%,6.0-6.5%, 6.5-7.0%, 7.0-7.5%, 7.5-8.0%, or 8.0-8.5%, balance unavoidableimpurities including up to 0.035% P, up to 0.015% S and up to 0.250% N.

In order to achieve tensile rupture strengths of at least about 50 ksiover a temperature range of room temperature to 1200° F., the J580 alloycan have about 0.4 to about 0.6% C, about 4.0 to about 5.0% Si, about0.7 to about 1.2% Mn, about 0.5 to about 4.0% Ni, about 11 to about 20%Cr, about 19 to about 23% Mo, about 1.0 to about 1.5% W, about 1.5 toabout 4.5% V, about 26 to about 35% Co, about 16 to about 24% Fe, about0.1 to about 1.6% Nb, balance unavoidable impurities including up to0.035% P, up to 0.015% S and up to 0.250% N. To achieve tensile rupturestrengths of at least about 70 ksi over a temperature range of roomtemperature to 1200° F., the J580 alloy can have about 0.45 to about0.55% C, about 4.2 to about 4.7% Si, about 0.7 to about 0.8% Mn, about2.5 to about 3.5% Ni, about 13 to about 15% Cr, about 21 to about 22%Mo, about 1.1 to about 1.3% W, about 1.3 to about 1.7% V, about 33 toabout 37% Co, about 15 to about 18% Fe, about 1.0 to about 1.4% Nb,total V plus Nb of about 2.5 to about 2.9%, balance unavoidableimpurities including up to 0.035% P, up to 0.015% S and up to 0.250% N.

The preferred embodiments are merely illustrative and should not beconsidered restrictive in any way. The scope of the invention is givenby the appended claims, rather than the preceding description, and allvariations and equivalents which fall within the range of the claims areintended to be embraced therein.

What is claimed is:
 1. A cobalt-rich wear resistant and corrosionresistant alloy comprising, in weight %: about 0.1 to about 0.8% C;about 0.1 to about 1.5% Mn; about 3 to about 5% Si; about 10 to about20% Cr; about 5 to about 32% Fe; about 0.5 to about 4% W; about 19 toabout 30% Mo; about 0 to about 20% Ni; about 20 to about 40% Co; up toabout 6% V; up to about 3% Nb; total V plus Nb of about 0.5 to about8.5%; and balance unavoidable impurities.
 2. The alloy of claim 1,wherein C is about 0.2 to about 0.5%, Mn is about 0.2 to about 0.8%, Siis about 3.5 to about 4.5%, Cr is about 13 to about 20%, Fe is about 12to about 32%, W is about 1 to about 4% W, Mo is about 19 to about 28%,Ni is about 0 to about 5%, Co is about 20 to about 35%, V is about 3 toabout 4%, and Nb is about 1 to about 2%.
 3. The alloy of claim 1, havinga microstructure comprising matrix phases of cobalt solid solution andLaves phases and uniformly distributed MC type carbides in the cobaltsolid solution matrix.
 4. The alloy of claim 3, wherein the solidsolution matrix is a face-centered cubic solid solution with NbC and/orVC precipitates therein.
 5. The alloy of claim 3, further comprisinginterdendritic primary eutectic phases.
 6. A valve seat insert made ofthe alloy of claim
 1. 7. The valve seat insert of claim 6, wherein C isabout 0.18 to about 0.52%, Mn is about 0.7 to about 1.2%, Si is about3.5 to about 4.6%, Cr is about 11 to about 15%, Fe is about 16 to about27%, W is about 1 to about 1.5%, Mo is about 19 to about 23%, Ni isabout 0.7 to about 4%, Co is about 26 to about 36%, V is about 1.3 toabout 4%, and Nb is about 1.2 to about 2.3%.
 8. The valve seat insert ofclaim 6, wherein the valve seat insert is a casting and themicrostructure includes 40 to 60% by volume Laves phases and 40 to 60%by volume cobalt solid solution phases.
 9. The valve seat insert ofclaim 6, wherein the valve seat insert has an as-cast hardness fromabout 50 to about 66 Rockwell C at 75 to 1000° F., a compressive yieldstrength from about 100 ksi to about 150 ksi from 75 to 1000° F.; and/oran ultimate tensile strength from about 70 ksi to about 100 ksi from 75to 1000° F.
 10. The valve seat insert of claim 6, wherein C is 0.2 to0.5%, Mn is 0.2 to 0.8%, Si is 3.5 to 4.5%, Cr is 13 to 20%, Fe is 12 to32%, W is 1 to 4% W, Mo is 19 to 28%, Ni is from 0 to 5%, Co is 20 to35%, V is 3 to 4%, and Nb is 1 to 2%.
 11. The valve seat insert of claim6, wherein the valve seat insert exhibits a dimensional stability ofless than about 0.25×10⁻³ inches per inch of insert outside diameter(O.D.) after about 20 hours thermal soaking at about 1200° F.
 12. Thevalve seat insert of claim 6, wherein the valve seat insert exhibits adecrease in hardness of 10% or less when heated from about roomtemperature to about 1000° F.
 13. A method of manufacturing an internalcombustion engine comprising inserting the valve seat insert of claim 6in a cylinder head of the internal combustion engine.
 14. The method ofclaim 13, wherein the engine is a diesel engine.
 15. A method ofoperating an internal combustion engine comprising closing a valveagainst the valve seat insert of claim 6 to close a cylinder of theinternal combustion engine and igniting fuel in the cylinder to operatethe internal combustion engine.
 16. The method of claim 15, wherein theengine is a diesel engine.
 17. The method of claim 15, wherein thevalve: (i) is composed of a high-temperature, nickel-chromium alloystrengthened by precipitation hardening; or a high-temperature,nickel-based superalloy; or (ii) the valve is hard-faced with a hightemperature, wear-resistant cobalt-based alloy strengthened by carbides;or is hard-faced with a high-temperature, wear-resistant cobalt-basedalloy strengthened by Laves phases.
 18. A method of making a cobalt-richwear resistant and corrosion resistant alloy according to claim 1wherein the alloy is melted and cast from a melt at a temperature offrom about 2800 to about 3000° F.; or the alloy is pre-alloyed powderwhich is compressed into a shaped component and sintered at atemperature from about 2000 to about 2350° F.
 19. The method of claim18, wherein the alloy is cast from a melt at a temperature from about2875 to about 2915° F.; the method further comprising heating the castalloy at a temperature from about 1300 to about 1500° F. for about 2 toabout 10 hours in an inert, oxidizing, reducing atmosphere or in avacuum.